“The fact that half to three-quarters of the evidence the FBI used to unleash the most awesome of surveillance powers upon Donald Trump’s inner circle came from sources tied directly to his Democratic opponent should worry us all, especially when that happened during an election,” said one senior Republican directly familiar with the evidence, describing the party’s core concerns.

“The FBI allowed itself to be used by Clinton partisans to parlay single-sourced, mostly unverified evidence into a counterintelligence probe with clear weaknesses that weren’t disclosed,” the source added.